This invention relates to ultrasonic vibration probes. More particularly, this invention relates to such an ultrasonic probe or horn that is particularly useful in the simultaneous sonication of biological and cellular materials disposed in multiple wells of a tray.
It has been well known for decades that a probe that vibrates at ultrasonic frequencies (i.e. frequencies greater than 16,000 Hz) and has its distal end submerged under fluids will create cavitation bubbles if the amplitude of vibration is above a certain threshold. Many devices have been commercialized which take advantage of this phenomenon. An example of such an ultrasonic cellular disrupter is disclosed in the Sonicator™ sales catalog of Misonix Incorporated of Farmingdale, N.Y. In general, devices of this type include an electronic generator for producing electrical signals with frequencies ranging from 16 to approximately 100 KHz, a piezoelectric or magnetostrictive transducer to convert the signal to mechanical vibrations and a probe (a.k.a. horn or velocity transformer) which amplifies the motion of the transducer to usable levels and projects or removes the operating face away from the transducer itself. The design and implementation of these components are well known to the art.
The cavitation bubbles produced by such ultrasonic vibration devices can be utilized to effect changes in the fluid or upon particles suspended therein. Such changes include biological cell disruption, deagglomeration of clumped particles, emulsification of immiscible liquids and removal of entrained or dissolved gases, among many others.
Cell disruption has been a particularly good application for probe type devices, in that the cells may be disrupted without the heat or cellular changes which prevent further analysis by conventional methodology. Many scientific protocols have been written which name the Sonicator™ (or similar devices) as the instrument of choice for the procedure.
In one device for ultrasonically processing multiple small samples, the Cup Horn™ manufactured by Misonix, Inc., of Farmingdale, N.Y., a probe tip is separated from the sample by a membrane or other solid surface. If liquid is present on both sides of the membrane or surface, the acoustic waves will propagate through the membrane and transfer the cavitation forces to the second liquid volume. This membrane does not have to be elastic. In fact, experience shows that glass or hard plastic is an acceptable material. Consequently, glass and plastic test tubes and beakers are routinely used in this service.
These Cup Horn devices are used primarily where the biological cells or molecules are easy to disrupt, such as liver or brain cells. With more tougher cells such as heart muscle or e-coli cells, the Cup Horns typically do not induce sufficient acoustic power into the tray wells since the energy must pass through the coupling fluid and membrane of the tray itself. It is therefore desired to come up with a device which induces sufficient acoustic energy into each of the wells of the tray horn simultaneously, reducing the time to treat the entire sample.
Some embodiments have been proposed or have been offered for sale for this purpose. In these embodiments, a half wave coupling block has been fashioned to which several daughter probes have been attached, with the center location of each coinciding with the center to center dimension of the tray wells. These devices have typically been very unwieldy in that their length is generally that of a full wavelength of the speed of sound in titanium. For a 20 kc system this is approximately 11 inches. Add the length of the transducer to it and an overall length of 18 inches or more is obtained.
In addition, these devices could only treat up to about 10 wells at most simultaneously, with most being significantly less than that. When greater numbers of probes were added, the uniformity of vibration suffered, in that one probe would be vibrating at a higher amplitude than the next, causing uneven yields within the wells themselves. In addition, the efficiency of vibration of these devices was low, thereby inducing thermal heating of the samples by the insertion of the hot probe.
Therefore, it is desired to obtain a device which can treat all 96 wells at one time with an invasive probe to provide sufficient acoustic energy in every well to break up the hardest biological cells, while providing equal amplitude per invasive probe all at less than a full wavelength of frequency, excluding the transducer itself.